The present invention relates generally to a system which can be used when an interventional procedure is being performed in a stenosed or occluded region of a blood vessel to substantially retain the unexpanded axial dimension of an expandable interventional instrument upon expansion thereof. The system of the present invention is particularly useful when performing stenting procedures in critical vessels, such as the carotid arteries.
A variety of non-surgical interventional procedures have been developed over the years for opening stenosed or occluded blood vessels in a patient caused by the build up of plaque or other substances on the walls of the blood vessel. Such procedures usually involve the percutaneous introduction of the interventional device into the lumen of the artery, usually through a catheter. One widely known and medically accepted procedure is balloon angioplasty in which an inflatable balloon is introduced within the stenosed region of the blood vessel to dilate the occluded vessel. The balloon catheter is initially inserted into the patient""s arterial system and is advanced and manipulated into the area of stenosis in the artery. The balloon is inflated to compress the plaque and press the vessel wall radially outward to increase the diameter of the blood vessel.
Another procedure is laser angioplasty which utilizes a laser to ablate the stenosis by super heating and vaporizing the deposited plaque. Atherectomy is yet another method of treating a stenosed blood vessel in which a cutting blade is rotated to shave the deposited plaque from the arterial wall. A vacuum catheter is usually used to capture the shaved plaque or thrombus from the blood stream during this procedure.
In another widely practiced procedure, the stenosis can be treated by placing an expandable interventional instrument such as an expandable stent into the stenosed region to hold open and sometimes expand the segment of blood vessel or other arterial lumen. Stents are particularly useful in the treatment or repair of blood vessels after a stenosis has been compressed by percutaneous transluminal coronary angioplasty (PTCA), percutaneous transluminal angioplasty (PTA) or removal by atherectomy or other means. Stents are usually delivered in a compressed condition to the target site, and then are deployed at the target location into an expanded condition to support the vessel and help maintain it in an open position.
Prior art stents typically fall into two general categories of construction. The first type of stent is expandable upon application of a controlled force, often through the inflation of an expandable member such as an expandable balloon in a dilatation catheter which, upon inflation of the balloon or other expansion means, expands the compressed stent to a larger diameter to be left in place within the artery at the target site. The second type of stent is a self-expanding stent formed from, for example, shape memory metals or super-elastic nickel-titanum (NiTi) alloys, which will automatically expand from a compressed state when the stent is advanced out of the distal end of the delivery catheter into the body lumen. Such stents manufactured from expandable heat sensitive materials allow for phase transformations of the material to occur, resulting in the expansion and contraction of the stent.
Self-expanding stents are typically delivered to an interventional procedure site for deployment thereof mounted on a delivery system and constrained in the sheath, to prevent the elastic nature of the self-expanding stent from causing it to expand prematurely. Once in position at the interventional procedure site, the sheath is retracted, enabling the stent to expand and deploy. However, there are problems associated with the retraction of the sheath for enabling deployment of the self-expanding stent. When the sheath is retracted during stent deployment, axial forces are generated in the stent when one end of the stent is fully open and the other end is still constrained. The stent is biased to slip out from under the sheath and finish deploying. An abrupt shortening that occurs as the stent deploys also generates axial forces. These axial forces can cause the stent to move in the distal direction during deployment and not properly cover the lesion as desired.
What has been needed is a reliable system and method for delivering an interventional device for treating stenosis in blood vessels which improve the accuracy of stent deployment over the lesion to be treated, while preventing axial movement of the stent during retracting of the sheath from extending thereabout. The system and method should be capable of enabling the stent to expand, while precisely placing the stent over the lesion to be treated. The system and method should be relatively easy for a physician to use. Moreover, such a system should be relatively easy to deploy and remove from the patient""s vasculature. The inventions disclosed herein satisfy these and other needs.
The present invention provides a system and method for treating an entire affected area in a blood vessel during the performance of a therapeutic interventional procedure, such as a balloon angioplasty or stenting procedure, while preventing adverse effects to surrounding tissue. The present invention is particularly useful when performing an interventional procedure in vital arteries, such as the carotid arteries, including the main blood vessels leading to the brain or other vital organs. As a result, the present invention provides the physician with a higher degree of confidence that an entire lesion will be treated, and that healthy tissue will not be adversely affected by the stenting procedure.
The present invention enables an interventional procedure to be performed in a blood vessel at the site of a lesion at an interventional procedure site, such that axial movement of a stent is prevented during retraction of a sheath extending thereabout, and the stent is accurately deployed at the interventional procedure site to treat the lesion.
In the present invention, the system includes a catheter for positioning in a blood vessel at an interventional procedure site, an interventional device located at a distal end portion of the catheter for expanding and deploying in the blood vessel at the interventional procedure site, an extendable member adapted to be extendable about the interventional device and retractable relative thereto, and a movement preventing element for preventing axial movement of the interventional instrument during retraction of the extendable member.
In an embodiment of the present invention, the system includes a catheter, including an elongated shaft having a distal end portion adapted to be positioned in a blood vessel at an interventional procedure site, and a support region proximate the distal end of the elongated shaft. An interventional instrument is adapted to move between a collapsed and expanded position in the blood vessel at the interventional procedure site, and to be supported on the support region of the elongated shaft. An extendable member is adapted to be extendable about the interventional instrument for delivery of the interventional instrument to the interventional procedure site, and to be retractable from extending about the interventional instrument for enabling the interventional instrument to expand at the interventional procedure site. A movement preventing element, for preventing axial movement of the interventional instrument in the support region of the catheter elongated shaft, during retraction of the extendable member from extending about the interventional instrument, enables deployment of the interventional instrument.
In another embodiment of the present invention, the system includes a catheter, including an elongated shaft having a distal end portion adapted to be positioned in a blood vessel at an interventional procedure site, and a support region proximate the distal end of the elongated shaft. An interventional instrument is adapted to move between a collapsed and expanded position in the blood vessel at the interventional procedure site, and to be supported on the support region of the elongated shaft, which interventional instrument includes a distal portion and a proximal portion. A movement preventing element, for preventing axial movement of the interventional instrument in the support region of the catheter elongated shaft, includes a distal element, adapted to be extendable about the distal portion of the interventional instrument, and a proximal element, adapted to be extendable about the proximal portion of the interventional instrument. The distal element and the proximal element are adapted to be extendable about the interventional instrument for delivery of the interventional instrument to the interventional procedure site, and to be retractable from extending about the interventional instrument for enabling the interventional instrument to expand at the interventional procedure site. The movement preventing element is further adapted to prevent axial movement of the interventional instrument during retraction of the distal element and the proximal element.